Purpose :
To evaluate intraocular lens (IOL) power calculation in eyes with keratoconus.

Methods :
Cases with a diagnosis of keratoconus and a history of cataract surgery, at 3 surgery centers, were retrospectively reviewed using patient charts. Accordingly, 27 eyes of 46 patients (mean age, 61.4±15.5 years) were included in the study. The average K value and axial length were 48.4±4.6 D and 25.4±1.8 mm, respectively. Various K values, IOL Master K value, corneal topography based third ring power(ring 3), average central corneal power over the central 3.0 mm based on corneal topography (ACCP 3 mm), total corneal power measured using anterior optical coherence tomography (Real power), average central corneal power over the central 3.0 mm calculated using OCT (Real ACCP) were used for IOL calculation. For each K value, the A-constant was optimized using the data from patients with normal cornea. The SRK/T formula was applied for the IOL power calculation. The postoperative refractive error for each K applied for IOL calculation was estimated using the refractive error 3 months after surgery. Friedman test was performed for statistical analyses, and Dunn’s multiple comparison test as a post-hoc test. A p value less than 5% was considered to be statistically significant.

Conclusions :
We could not determine the K value suitable for IOL power calculation in keratoconus eyes. However, variation in postoperative refractive error tended to be small when K value calculated with the total corneal power was used. Moreover, postoperative refractive error showed a hyperopic shift when K value calculated only with anterior corneal power was used, and a myopic shift with K value derived from total corneal power.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.